Electric steel-furnace.



J. L. DIXON.

ELECTRIC STEEL FURNACE.

APPLICATION man OCT 14. 1916.

1,214,764. .Batented Feb. 6,1917.

JOSEPH LA WTON DIXON, 0F DETROIT, MICHIGAN.

ELECTRIC STEEL-FURNACE.

Specification of Letters Patent.

rammed Feb. 6, 1917.

Application filed October 14, 1916. Serial No. 125,559.

To all whom it may concern Be it known that l, Josnrn L. D1XoN,'a subject of the King of Great Britain, residing. at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Electric Steel-Furnaces; and'I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention has particular ref-- crence to electrical metallurgical furnaces, and especially to steel. furnaces, of the type in which the arcs which supply the heat are formed by currents passing from and to movable electrodes suitably suspended above the bath or material acted upon. In other words my. invention has reference to elec-.

trical arc furnaces wherein the crucible is not included within. the electric circuit.

The principal object of the invention is to supply a simple and effective means whereby regulation of the positions of the electrodes, either automatically or by hand may be rendered more simple and certain.

In'the accompanying drawings, Figure 1 is a diagram illustrating a proposed arrangement of parts for steel furnaces of the above named type, and Fig. 2 is a similar view illustrating my improvement.

It'has been proposed to construct furnaces of the type in question wherein two phase currents are supplied through four movable electrodes above the material to be treated. Such a plan is illustrated in Fig. 1 of the accompanying drawings, wherein three phase current is delivered over the mains 10, 11 and 12 to two Scott-connected transformers whose primaries are shown at 13,

and 14 and whose secondaries 15 and 16, supply currentof very high amperage to the four electrodes 17 18, 19 and 20. The bath or material to be actcd'upon, shown at 21, is carried by a suitable crucible 22.

For reasons well understood, it is highly desirable to preserve uniform heating con ditions by keeping the lengths of the four arcs formed under the electrodes as nearly equal as possible.

It will be seen that each pair of electrodes, 17, 18 and 19, 20 respectively, be-

longs virtually to an independent single.

phase circuit, since all the current passing through either member of either pair finds its way back through the other member of the same pair. The consequence is that either 17 or 18 may be much nearer the bath 21 than the other member of its own pair, and may indeed be inactual contact with the bath, thereby extinguishing the arc beneath it, without necessarily betraying the fact through an ammeter. This follows from the fact that the increased length of one of a pair of such arcs may well compensate for the decrease in length of the other are, thereby producing the same total resistance as existed when the arcs were equal. It is equally clear that, in such an arrangement, even if an ammeter placed in either circuit (17, 18 or 19, 20) shows a variation in current the change will have no significance, since it will not indicate which electrode should be raised or lowered. These considerations apply whether automatic or hand regulation is employed. lonsequently, where such an arrangement is used the combined indications of ammeters and voltmeters must be referred to in accomplishing regulation. This complicates the problem of both hand and automatic regulation and makes proper ellicient handling quite difficult.

I have found that by supplying an electrical connection, as by the conductor 23, in Fig. 2, between the neutral points of the two secondaries 15 and 16, the necessity for voltmeter or potential readings or control is entirely obviated, and the problem of regulation can thus be reduced to a simple ampere or current volume reading or control.

By employing the connection 23' in the manner indicated, the current leaving any one of the four electrodes 17, 18, 19 or 20 does not return exclusively through the single electrode which is directly connected to the same secondary as itself. The consequence is that, if the electrode 17, for Insta-nce, approaches too near to the bath 21, thus shortening its arc, a single ammeter related exclusively to its appropriate supply conductor will indicate an increase ofcurrent and betray the fact that one certain electrode is too near the bath.

I have indicated the four separate and independent ammeters diagrammatically at 2 1-, 25,26 and 27, in Fig. 2. It is to be understood, of course, that these stand merely as indications of such apparatus, operated simply by variations in current strength,

the positions of the electrodes by any Well known automatic system depending upon simple variations in current strength.

What I claim is i 1. In an arcing electric furnace of the type wherein the crucible forms no part of the circuit, two pairs of arcing electrodes, a suitable two-phase transformer connected therewith through two secondaries, and an'electric connection between the neutral points of said secondaries.

2. In an arcing electric furnace of the type wherein the crucible forms no part of the circuit, two pairs of arcing electrodes, a transformer primary and secondary for each pairof electrodes so connected therewith as to supply two phase current there to, a connection between the neutral points of the two secondaries and independent controlling devices of the annneter type in electric relation with the respective leads of said electrodes and said devices.

ltn testimony whereof, I affix my signature.

JOSEPH LAWTON DIXQN. 

